I did a search for this and couldn't find anything, but wasn't sure what to search under.
The bug is when I have an AV under water, a strange shape seems to appear in front of it. The following two images show this from front and rear.


I made sure that before I took these shots that the AV had NO attachments that might be responsible for this. It doesn't happen with just Snowglobe so far as I know, and doesn't happen with any other viewer. The details of my main system are:
I have a second PC with this installed, and the bug does
not appear on that one (I mostly use the two to make webcomics from SL):
I also have an older version of Cool Viewer installed on the main PC I use -- Cool VL Viewer 1.23.5 (24) Aug 14 2010 16:14:54 (Cool VL Viewer) -- and it doesn't have this problem.